Infectious Disease, Public Health & Health IT

Category Archives: Influenza

The past few weeks are finally beginning to show a declining trend in the number of cases with influenza like illness (ILI) presenting to the ER . The last wave appears to have peaked the week of Oct 12-18 when we saw about 17% of visits to the ER having an ILI. The week of Nov 9-15 had 6% of visits with ILI. This week may be even lower. This is a welcome relief from the peak levels of mid Oct.

Nationally the same declining trend appears to be taking place with fewer states reporting active H1N1.

Does this mean that the season is over or that vaccination is not necessary? The answer is no to both.

Influenza does come in “waves”. We had a wave over spring break and another in Oct. We may get another wave in the next month or so. Having enough herd immunity through vaccination can minimize the wave by decreasing the number of susceptible individuals in the community. Remember the vaccination is of greater benefit for the community than for the individual. We all go a long way in protecting those who cannot protect themselves. So those who have not gotten their vaccinations should still do so.

On a side note; We are continuing to have intensive care hospitalizations due to influenza related complications. This week we have two otherwise healthy individuals between the ages of 45-50 with severe pneumonia related complication in the ICU. Both cases have been ill for over a month before seeking medical help. Both would have been infected during the last wave of influenza. Neither of them were vaccinated.

Remember even though the wave may have past. There are still people that may still be suffering from delayed complications.

1. H1N1-2009 is the dominant influenza in circulation
2. Most isolates appear to be sensitive to Oseltamivir (tamiflu)
3. Outpatient visits for influenza like illnesses is higher than expected for this time of year (7.7% instead of 2.3%)
4. 672 deaths occurred due to lab confirmed H1N1 related illness in this time frame.

What Gullian barre? Guillain barre sydrome is a neurologic condition where the body immune systems antibodies misrecognizes parts of the nervous system as foreign and attacks it. The host can develop muscle weakness and even paralysis. This can be a serious condition. Fortunately it is very rare. This is NOT caused directly by a vaccine but by the immune system itself. This can therefore happen with anything that stimulates the immune system to produce more antibodies. In other words infection itself can produce GBS. Most GBS is caused by viral infections and by a common bacteria that causes food poisoning called Campylobacter.

There are about 10-20 cases of GBS per million population in any given year, this is known as the “background rate” of occurrence. This has been closely watched since the initial cases of GBS were reported in the 1970s and does not appear to have changed that much with subsequent influenza seasons. (Roper AH. The Guillain barre syndrome. N Engl J Med 1992 326:1130-6)

The first series of GBS related to vaccination was reported in JAMA in 1980. This was based on data collected from the 1976 influenza vaccination season where it was believed that people were getting GBS from the vaccination. In this study they cite an attributable risk of 13 cases of GBS per 100,000 population vaccinated (an alarmingly high number) based on a collection of 32 cases with a history of vaccination. They needed a background rate for comparison. Due to the lack of public health records for GBS at that time they called local neurologists on the roster of the local medical associations in the state of Ohio and asked them about all the cases they had seen in the studied time interval. With this information they arrived at a background prevalence of 2.6 cases per 100,000. Of course this data was met with appropriate alarm, it turned out to be a public relations fiasco.

More detailed studies of the initial finding were later published regarding the 1976 swine flu vaccination where 40 million people were vaccinated and possible 532 cases of Guillian Barre were reported and 32 people died. This gives a rate of
about 13 cases per million. One tenth the number originally cited in the smaller study and a number more in the middle of the expected background rate. Definitely less alarming.

The risk from vaccination therefore may add an additional risk of perhaps up to 1 additional case per 1,000,000 administered doses of influenza vaccine this is a very small number compared with the original 130 cases per 1,000,000 that was reported in the 1980 article. This is rare enough to go so far as to say that there is probably no causal relationship influenza vaccination and GBS.

The question of vaccination for Influenza (H1N1) in pregnancy is frequently asked. A small study published by NIH does provide some answers around this.

Why all the concern about pregnancy?
To date there have been 100 pregnant women hospitalized with H1N1 in the US this season. 28 deaths have occurred in this group. This is an alarmingly high proportion for this healthy group (28% of admissions!). Though the total numbers seem very small it is the proportion of deaths in this important group that is high. Why is this group more important than other? To say the obvious; too many other lives depend on these women. A pregnant women is likely to have other children at home, those children are not only at risk for illness from mother but if mother is incapacitated or worse dies can changes the social structure of the home and future lives of her young children. Loss of life in other groups of people as traumatic as it may be does not carry as great a social burden as losses in this group can. This group is therefore at highest priority to be vaccinated.

Do pregnant women have adequate response to vaccination?
The study does show that pregnant women do mount an adequate response to a single dose of inactivated injectable vaccine and it is well tolerated. The 15mcgm dose appears to provide adequate response in 92% of recipients and 30mcgm in 96% of recipients. the pool sizes were very small at 25 women in each group.

The H1N1 2009 vaccine is made in an identical process to the existing seasonal influenza vaccine. It is a killed vaccine, therefore cannot cause H1N1. It is also thiomersal free.

“I got sick the day after I got vaccinated, the vaccine does not work!” is a common statement of alarm that frequently comes to me. Please understand that this is neither a failure of the vaccine nor caused be the vaccination itself.

Remember that the vaccine itself does not kill influenza. The vaccine stimulates your immune system to be ready for influenza if it were to encounter it in the future. This preparation or training takes about 2 to 4 weeks. Therefore there is some potential to get the “real” illness early after vaccination, though even that should be milder than if one was not vaccinated.

So if someone at home gets ill in the days after you got your vaccination, do not blame the vaccine. We are in the depths of flu season it is more likely than not that little johnny got infected at school than from your dead vaccination.

If there is one good thing that has come out of this flu season then it is the awareness of vaccination. In years past, on the average we have had 45% vaccine coverage for hospital employees. This has been abysmally low to offer any real herd immunity. This year with an aggressive proactive approach with formal lectures and informal face to face discussions with groups of hospital staff discussing the benefits, myths. We have a record >75% seasonal vaccine coverage. Most of the recipients were taking influenza vaccine for the first time. We may actually run out of seasonal vaccine for the first time.

With regards to H1N1, we did start with live attenuated intranasal last week and had a high acceptance rate among those who qualified. Unfortunately many of the motivated staff did not qualify. This week we did receive inactivated injectable vaccine. The acceptance rate for this has been very good. I did need to go on an education round in the hospital and answer more question. But once a few staff members got motivated more and more followed. I think we will have a good coverage for H1N1 too.

Some factors promoting better acceptance may be the larger numbers of 20-49 year olds that are coming to the hospital with moderate to severe viral pneumonia. A few have required intensive care management. The number of patients coming to the ER with influenza like illness (ILI) has seen a sharp spike in the past week. The proportion of ILI that are influenza A positive has gone up from 3-5% in the weeks of Oct 5th and 12th to 18% in the week of Oct 19th.

So far very few complaints about getting vaccinated aside from the minor injection site aches and pains.

There are more cases of influenza like illness this year than expected. Also the number of deaths are higher than expected for this time of year. 69% of the 12,900 samples sent to the reference labs are positive for 2009 H1N1. Remember that most of these samples are from persons ill enough to be hospitalized. This does not report all infected cases as ambulatory persons are not being screened due to overwhelming demand for tests. The vast majority of cases probably do not need hospitalization. Therefore the number of cases of H1N1 likely to be much higher.

Almost all isolates of 2009 H1N1 are showing a good match to the current vaccine. Remember that the virus does tend to have high mutation rate making 100% coverage difficult.

For the most part H1N1 is showing susceptibility to Oseltamivir (Tamiflu).

Total number of pediatric deaths is now 95 cases nation wide for 2009 H1N1.

See the graph showing the unusual spike in outpatient visits for influenza like illness towards the right of the graph.

I did get my H1N1 2009 live attenuated intranasal vaccination on 10/22/09. It was really no big deal, took less than 5 minutes to do. I feel fine today.
I also took the inactivated injectable seasonal vaccination on 10/14/2009. I also vaccinated my family with the same formulation that night. Aside from some arm soreness that my 9 year old complained of, no one has had any complaints.

Pregnant women are at higher risk of hospitalization and death from influenza.
Though Oseltamivir is category C due to lack of trials in this group, it has been used successfully in all stages of pregnancy.
All pregnant women with influenza like illness (ILI) should be started on oseltamivir as early as possible.
Do not wait for lab confirmation before initiating treatment.
If pregnant women is exposed to known case of influenza a 10 day course of oseltamivir may be indicated as prophylaxis.
Prevention with vaccination with inactivated injectable vaccine is indicated in all pregnant women.CDC reference for details